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mmc: sdhci: Disable SD card clock before changing parameters 

Per the SD Host Controller Simplified Specification v4.20 §3.2.3, change
the SD card clock parameters only after first disabling the external card
clock. Doing this fixes a spurious clock pulse on Baytrail and Apollo Lake
SD controllers which otherwise breaks voltage switching with a specific
Swissbit SD card. This change is limited to Intel host controllers to
avoid an issue reported on ARM64 devices.

Signed-off-by: Kyle Roeschley <kyle.roeschley@ni.com>
Signed-off-by: Brad Mouring <brad.mouring@ni.com>
Signed-off-by: Erick Shepherd <erick.shepherd@ni.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20250724185354.815888-1-erick.shepherd@ni.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Erick Shepherd 2025-07-24 13:53:54 -05:00 committed by Ulf Hansson
parent c17b750b3a
commit 5f755ba95a
1 changed files with 13 additions and 2 deletions
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15
drivers/mmc/host/sdhci-pci-core.c
View File

@ -679,8 +679,19 @@ static int intel_start_signal_voltage_switch(struct mmc_host *mmc,
return 0;
}
static void sdhci_intel_set_clock(struct sdhci_host *host, unsigned int clock)
{
u16 clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
/* Stop card clock separately to avoid glitches on clock line */
if (clk & SDHCI_CLOCK_CARD_EN)
sdhci_writew(host, clk & ~SDHCI_CLOCK_CARD_EN, SDHCI_CLOCK_CONTROL);
sdhci_set_clock(host, clock);
}
static const struct sdhci_ops sdhci_intel_byt_ops = {
.set_clock = sdhci_set_clock,
.set_clock = sdhci_intel_set_clock,
.set_power = sdhci_intel_set_power,
.enable_dma = sdhci_pci_enable_dma,
.set_bus_width = sdhci_set_bus_width,
@ -690,7 +701,7 @@ static const struct sdhci_ops sdhci_intel_byt_ops = {
};
static const struct sdhci_ops sdhci_intel_glk_ops = {
.set_clock = sdhci_set_clock,
.set_clock = sdhci_intel_set_clock,
.set_power = sdhci_intel_set_power,
.enable_dma = sdhci_pci_enable_dma,
.set_bus_width = sdhci_set_bus_width,